Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$185.84	5.659%	$196.3567	$196.36	$196.35	$196.40
Purchase #2	$246.62	11.149%	$274.1157	$274.12	$274.10	$274.10
Purchase #3	$30.77	3.296%	$31.7842	$31.78	$31.80	$31.80
Purchase #4	$138.25	7.348%	$148.4086	$148.41	$148.40	$148.40
Purchase #5	$134.92	9.483%	$147.7145	$147.71	$147.70	$147.70
Purchase #6	$130.72	5.127%	$137.422	$137.42	$137.40	$137.40
Purchase #7	$97.59	12.427%	$109.7175	$109.72	$109.70	$109.70
7 purchase totals =	$964.71		$1,045.5192	$1,045.52	$1,045.45	$1,045.50